Don't Say a Word (Hometown Antihero #2)
Amber Lynn Natusch

When rookie FBI agent Cedric Dawson returns to town to finish an open investigation, he goes undercover at her high school—as her ex. Determined to keep her from interfering, Dawson’s plan backfires after Ky gets an anonymous call about missing girls officially labeled as runaways—runaways that didn’t really run away at all.
Because dead girls can’t run.
And they don’t say a word.